Curable compositions

ABSTRACT

Compositions comprising A. A DIGLYCIDYL ESTER OF FORMULA   AND B. A POLYCARBOXYLIC ANHYDRIDE OF FORMULA   WHERE, IN EACH FORMULA, ONE OF R1 to R6 is a hydrogen atom or a methyl or allyl group and the remaining R&#39;&#39;s denote hydrogen atoms, on being cured, show a very high thermal resistance and may be used as laminating resins, surface-coating resins, dipping resins, casting resins, adhesives, and potting and insulating materials for the electrical industry.

United States Patent [191 Hope et al.

[ Oct. 9, 1973 CURABLE COMPOSITIONS [75] Inventors: Paul Hope, Walden;Richard John Martin; Bernard Peter Stark, both of Cambridge, all ofEngland [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed:Nov. 17, 1971 [21] Appl. No.: 199,786

[30] Foreign Application Priority Data Nov. 19, 1970 Great Britain55,106/70 [52] US. Cl 260/78.4 EP, 260/2 EP, 260/2 EA [51] Int. Cl C08g30/12 [58] Field of Search 260/2 EP, 2 EA, 78.4 EP, 260/346.3,'348 R,348 A [5 6] References Cited UNITED STATES PATENTS 3,598,749 8/1971Cheng et al 252/182 FOREIGN PATENTS OR APPLICATIONS 2,000,323 9/1969France Primary Examiner-Joseph L. Schofer Assistant Examiner-John KightAttorney-Karl F. Jorda et a1.

[57] ABSTRACT Compositions comprising a. a diglycidyl ester of formulaand b. a polycarboxylic anhydride of formula CO R 1 I I a- Ro O Ra CO/ 6Claims, No Drawings CURABLE COMPOSITIONS This invention relates tocurable compositions containing a diglycidyl ester of bicyclo[2.2.llheptenedicarboxylic acid.

It is known that epoxide resins (which are substances containing morethan one 1,2-epoxide group per molecule) can be cured, i.e., convertedinto insoluble, infusible, cross-linked materials. These materials havevaluable technical properties. Particularly when polycarboxylic acids ortheir anhydrides are used as the curing agents, products with a highdegree of resistance to elevated temperatures can be obtained. However,the compositions hitherto available in general do not meet the morerigorous requirements of resistance to heat.

We have now found that, by choice of certain combinations of epoxideresins, viz. diglycidyl bicyclo[2.2.l hept-S-ene-2,3-dicarboxylates, andcuring agents, there can be made compositions which, on being cured,exhibit very high thermal resistance, as shown by the level of theirtemperatures of deflection under load.

This invention accordingly provides curable compositions comprising:

a. a diglycidyl ester of formula I! e -30 R where, in each formula, oneof R to R is a hydrogen atom or a methyl or allyl group and theremaining Rs denote hydrogen atoms. I

There are also provided the products obtained by curing suchcompositions.

Diglycidyl bicyclo[2.2.l ]hept--ene-2,3- dicarboxylate is a knowncompound (see e.g., German Auslegeschrift No. 1,245,369), and isobtainable by reaction of maleic anhydride with cyclopentadiene to formbicyclo[2.2.1]hept-S-ene-2,3-dicarboxylic anhydride followed byconversion of the latter into its diglycidyl ester by conventionalmethods. Similarly, methylcyclopentadiene or allylcyclopentadiene yield,with maleic anhydride, the bicyclic anhydride which, too, can beconverted into the diglycidyl ester. Diglycidylallylbicyclo[2.2.1]hept-5-ene-2,S-dicarboxylate is believed to be a newcompound. (It will be appreciated that no specific location can beassigned for the methyl or allyl group in methycyclopentadiene orallycyclopentadiene, since the commercial materials consist of mixtureswhich may isomerise; from this it follows that specific locations cannotbe assigned in the adducts with maleic anhydride, either).

The compositions may contain catalysts for the curing reaction; thesemay be tertiary amines, tertiary amine salts, complexes of tertiaryamines with boron trichloride, quaternary ammonium compounds, or sodiumalkoxides (e.g., 2,4,6-tris(dimethylaminomethyl)- phenol,N-benzyldimethylamine, imidazoles and their salts with fatty acids, suchas l-methylimidazole, 2- ethyl-4-methylimidazole, and l-methylimidazole2- ethylhexanoate, 4-aminopyridine, boron trichloridetrimethylaminecomplex, triamylammonium phenoxide, or the sodium derivative of2,4-dihydroxy-3- hydroxymethylpentane).

The proportions to be used of the anhydride and the diglycidyl ester canvary according to the particular requirements and the properties soughtof the curable and cured compositions: usually, from 0.6 to 1.1, andespecially from 0.75 to 0.95, anhydride equivalents of the carboxylicacid anhydride are used per 1,2-epoxide equivalent of the diglycidylester. To obtain high deflection temperature values, e.g., of 200 C orhigher, it is advisable to heat the compositions at a temperature of 175to 275 C for at least 1 hour.

The compositions of this invention may contain additives such asextenders, reinforcing agents and fillers, colouring matter, flowcontrol agents, flame inhibitors, and mould lubricants. Suitableextenders, reinforcing agents, and fillers are, for example, asphalt,bitumen, glass fibres, carbon fibres, asbestos fibres, mica, quartzflour, cellulose, kaolin, wollastonite, colloidal silica such as thatavailable under the registered Trade Mark Aerosil, and powdered metalssuch as aluminium. They may be used as laminating resins,surface-coating resins, dipping resins, casting resins, adhesives, andpotting and insulating materials for the electrical industry, and alsoin the manufacture of such products.

In the following Examples which illustrate the invention, parts are byweight (unless otherwise specified) and temperatures are in degreesCentigrade. Temperatures of deflection under load were determinedaccording to British Standard Specification 2782, Method 1026. The termMartens point, unless otherwise specified, denotes the heat deflectiontemperature under load as determined by a modification of the MartensD.I.N. procedure. A smaller sample, 76 mm X 19 mm X 3.2 mm (comparedwith a sample size of 120 mm X 15 mm X 10 mm specified in the D.I.N.procedure) and a maximum fibre stress of 12.5 kg./sq. cm. (compared withthe specified 50 kg./sq.cm) were employed. Such results, while notnecessarily the same as those which would be obtained by the originalD.I.N. procedure, are, however, mutually comparable.

The diglycidyl bicyclo[2.2.1]hept-5-ene-2,3- dicarboxylate used wasprepared as follows.

Bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (182g, 2 equiv.),epichlorohydrin (2,400 g, 26 equiv.) and tetraethylammonium bromide (3g) as catalyst were warmed with stirring in an atmosphere of nitrogen.At about an easily controllable exothermic reaction set in and thetemperature rose to 114, then fell and was maintained at 100 to for afurther hour, by which time the mixture was a clear, goldenyellowliquid. With the mixture at a temperature of 100, a solution of sodiumhydroxide (104 g, 2.6 equiv., i.e., 30 percent excess) in water (100 ml)was added dropwise, and the water introduced, together with that formedduring the reaction, was removed by azeotropic distillation.Epichlorohydrin removed was continuously returned to the reactionvessel, and the rate of adding the sodium hydroxide solution wastherefore dependent on the rate at which water could be removed from thereaction mixture. Addition took 100 to minutes 3 and, at completion, themixture was quickly warmed to 107, after which it was rapidly cooled inan ice bath. The volume of water removed from the reaction mixture was120 ml (calculated value 136 ml).

The mixture was filtered to remove sodium chloride and theepichlorohydrin was removed from the filtrate by distillation in vacuo.The residue was dissolved in benzene (1,000 ml), washed four times withan equal volume of water, and dried with anhydrous sodium sul phate.

Sodium sulphate was removed by filtration and the benzene was distilledoff in vacuo. The residue, consisting essentially of diglycidylbicyc1o[2.2.l]hept-5-ene- 2,3-dicarboxy1ate, was a golden brown liquidof medium viscosity and weighed 261g (calculated yield, 294g). it had anepoxide content of 5.61 equiv./kg. (82.5 percent of the calculatedvalue, 6.80 equiv./kg).

The diglycidyl methylbicyclo[2.2.l]hept-5-ene-2,3- dicarboxylate usedwas prepared as follows.

Methylbicyclo[2.2.l ]hept-5-ene-2,3-dicarboxylate anhydride (178 g, 2acid equiv.), epichlorohydrin (833 g, 9 equiv.) and water (72 g, '4equiv.) were warmed with stirring to 85 C and held at this temperaturefor 1 hour. A 50 percent aqueous solution of tetramethylammoniumchloride 10g) was then added, the mixture was heated to reflux and waterwas removed azeotropically. The pH of the solution, which was observedby means of an electrode immersed in the solution, rose steadily fromits original value of 1.0. When the pH value reached 7.6, the mixturewas quickly cooled and a further quantity of epichlorohydrin (833 g, 9equiv.) was added. The solution was then warmed with stirring under anatmosphere of nitrogen and at a temperature of 100 C, a solution ofsodium hydroxide (104 g, 2.6 equiv.) in water (100 ml) was addeddropwise, while the water introduced, together with that formed duringthe reaction, was removed azeotropically. At completion of the addition,which took about 60 minutes, the mixture was rapidly cooled and thesodium chloride was removed by filtration. The filtrate was washed oncewith an equal volume of water and dried over anhydrous sodium sulphate.The sodium sulphate was removed by filtration and the epichlorohydrinwas distilled off in vacuo. The residue, which consisted essentially ofdiglycidyl methylbicyclo[2.2.l]hept-b S-ene- 2,3-dicarboxylate, was agolden-brown liquid of medium viscosity and weighed 247g (calculatedvalue 308 g): its epoxide content was 4.95 equiv./kg (calculated value6.49 equiv./kg).

EXAMPLE 1 A mixture of diglycidyl bicyclo[2.2.l]hept-5-ene-2,3-dicarboxylate (1) (100 parts), methylbicyclo[2.2.l-]hept-5-ene-2,3-dicarboxylic anhydride (I1) (90 parts), andl-methylimidazole (1 part) as catalyst was heated for 16 hours at 100followed by for 2 hours at 150: the deflection temperature of theproduct was 115. On further heating the product for 2 hours at 260, thedeflection temperature rose to 283.

For purposes of comparison, a mixture containing 100 parts of diglycidylcyclohex-4-ene-l,2- dicarboxylate (111), i.e., the unbridged analogue ofI, 100 parts of 11 (a larger proportion of the curing agent beingrequired because of the higher epoxide content per unit mass of 111),and 1 part of methylimidazole was subjected to the same cure cycle.After being heated at 100 and then at 150", the samples had a deflectiontemperature of 120, i.e., 5 higher than those prepared from 1. But whenthe samples were heated further at 260, their deflection temperaturereached only 183, i.e., 100 lower than that of the cured compositions ofthis invention.

In other experiments, a mixture containing 100 parts of 1, parts of II,and 0.2 part of N-benzyldimethylamine was heated for 4 hours at then 2hours at and 2 hours at 260.The temperature of deflection under load ofthe cured specimen was more than 250. A mixture containing 100 parts ofl, 90 parts'of II, and 2 parts of imidazole 2-ethy1hexanoate was heatedfor 3 hours at 100, 2 hours at 150, and 4 hours at at which time thedeflection temperature of the specimen was 126: after the sample hadbeen exhaustively cured by being heated for a further 336 hours at 190C, its distortion temperature had risen to 244 C. On the other hand, thecorresponding values of samples prepared from 100 parts of III, 100parts of 11, and 2 parts of imidazole Z-ethylhexanoate were 129 and 155:this shows that, even with exhaustive curing, the deflection temperatureof the comparative sample never approached that of a sample preparedfrom a composition of this invention.

EXAMPLE 2 EXAMPLE 3 A mixture of 44 parts of diglycidylmethylbicyclo[2.- 2.1]hept-5-ene-2,3-dicarboxylate, 36 parts of (11),and 0.8 part of N-benzyldimethylamine was cured by heating for 4 hoursat 100, 2 hours at 145, and then at 260. The Martens point of the samplerose as follows:

after curing for Martens point (hours at 260) EXAMPLE 4 Compositionswere prepared as indicated in the following Table, and cured by heatingfor 1 hour at 100 C, 1 hour at 150 C, and the 2 hours at 260 C:

Parts by weight a b c (l e ene-2,3-dicarboxylate (I) Dlglycidyl0ye1ohex-4-ene-1, 2-

dicarboxylate (III) Diglycldyl ether of bisphenol A (5.2 epoxideequivJkg.) Methylbicyc1o[2.2.1]hept 5-ene- 2, 3-dicarboxylie anhydride(II). 90 100 Cyclohexane-l, 2-dicarboxy1ie acid auhydrideLmethylimidazole Deflection temperature, C

Weight loss after 14 days at 230 (1., percent (130 x 12 x 6 mm.specimens in a fanned oven) l Specimen ablated.

Composition a is a composition of this invention, while compositions b,c, d, and e were prepared for purposes of comparison. Composition bcontains the same epoxide resin, (I), as does a, but the anhydride useddoes not contain the bicyclo[2.2.1]hept-5-ene ring. Composition 0contains the anhydride II but the unbridged analogue of I, namely III;composition d contains the anhydride II and the most commonly employedepoxide resin, a diglycidyl ether of 2,2-bis(4- hydroxyphenyl)propane.Although compositions c, d, and e contain respectively, 100, 100, and 80parts by weight of the curing agent, the results obtained are comparableto those obtained with compositions a and b, the ratios employedreflecting the difference in epoxide content per unit weight of theepoxide resins and the molecular weights of the curing agents.

The product obtained by curing a composition of this invention, i.e.,composition a, had a very high heat deflection temperature under load:it also proved to have good electrical properties at high temperatures,the power factor at 1 kHz over the range 200 C being less than 0.01. Thethermal stability at 230 C was comparable with that of cured compositione, while having a far higher deflection temperature, and was much betterthan those of the products obtained by curing the comparablecompositions b and d.

We claim:

1. a curable composition comprising a. a diglycidyl ester of formula o 0o omen-0H1 and b. a polycarboxylic anhydride of formulawhere,ineachiorniifiaoneof?"tollisselectedfrom the group consisting of ahydrogen atom, a methyl and an allyl group, and the remaining Rs denotehydrogen atoms, in sufficient quantity to provide from 0.6 to 1.1anhydride equivalents per 1,2-epoxide equivalent of the diglycidyl ester(a).

2. The compositions according to claim 1, containing from 0.75 to 0.95anhydride equivalents of the carboxylic acid anhydride (b) perl,2-epoxide equivalent of the diglycidyl ester (a).

3. The compositions according to claim 1, comprising diglycidylbicyclo[2.2. l ]hept-5-ene-2,3- dicarboxylate and methylbicyclo[2.2.l]hept-5-ene2,3- dicarboxylic anhydride.

4. The compositions according to claim 1, comprising diglycidylbicyclo[2.2. l ]hept-5-ene-2,3- dicarboxylate andallylbicyclo[2.2.l]hept-5-ene-2,3- dicarboxylic anhydride.

5. The compositions according to claim 1, comprising diglycidylmethylbicyclo[2.2.l]hept-5-ene-2,3- dicarboxylate and methylbicyclo2.2.1 hept-5-ene-2,3- dicarboxylic anhydride.

6. Cured products obtained by heating a composition as claimed in claim1 at a temperature of from to 275 C.

2. The compositions according to claim 1, containing from 0.75 to 0.95anhydride equivalents of the carboxylic acid anhydride (b) per1,2-epoxide equivalent of the diglycidyl ester (a).
 3. The compositionsaccording to claim 1, comprising diglycidylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylate andmethylbicyclo(2.2.1)hept-5-ene2,3-dicarboxylic anhydride.
 4. Thecompositions according to claim 1, comprising diglycidylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylate andallylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic anhydride.
 5. Thecompositions according to claim 1, comprising diglycidylmethylbicyclo(2.2.1)hept-5-ene-2,3-dicarboxylate and methylbicyclo 2.2.1hept-5-ene-2,3-dicarboxylic anhydride.
 6. Cured products obtained byheating a composition as claimed in claim 1 at a temperature of from175* to 275* C.